A ball-point pen holds, at its front end, a small ball which receives frictional forces as writing and rotates on paper, to thereby draw ink out of a tube and transfer it onto the sheet.
As shown in FIG. 39, a structure `a` of a writing portion in a ball-point pen is generally composed of a ball `b` and a holder `d` rotatably holding the ball `b` on a socket seat `c`. This assembly made of the ball `b` and the holder `d` is called a tip `e`. The tip `e` is connected with an unillustrated refill as an ink reservoir, so that ink is supplied to the ball `b`.
Meanwhile, the ball-point pen accidentally becomes incapable of writing even with sufficient ink remaining in the refill. This kind of happening can be attributed to the following four causes:
1) One possible case is that ink is hardened from timeworn effects or metal surfaces inside the tip `e` are corroded whereby the rotation of the ball `b` is disturbed. This is liable to happen when the pen has been left unused for a prolonged period of time. PA1 2) A case where the ball-point pen is used excessively and the ball `b` is worn out and deformed so as to disturb smooth rolling of the ball `b`, or excessive use deforms a hold `g` at the front end of the ball socket seat in the holder `d` thereby inhibiting the rotation of the ball `b`. PA1 3) A case where, when the pen with dust and dirt collected in clearance `h` between the holder `d` and the ball `b` has been left for a prolonged period of time, these dust and dirt induce ink to dry and stick to the ball `b` and the holder `d`, whereby the rotation of the ball `b` is disturbed. PA1 4) A case where a gap is formed between the ball `b` and the ink in the refill and air enters the gap. In this case, the ball `b` itself can rotate, unlike the aforementioned cases 1) to 3) in which ink cannot come out due to the obstruction to the rotation of the ball `b`. Nevertheless, because the ball `b` is not in contact with ink, the ball `b` rotates in vain and cannot bring the ink which is in the refill to the paper surface. Such an idle rotation is liable to occur when the pen is used to write with its tip up. In this case, when the ball `b` uses up the ink therearound, the ink in the refill does not follow the rolling of the ball `b`, whereby a gap is created between the ball `b` and the ink. Accordingly, however does the ball `b` rotate, the ink in the refill will not come out. To make matters worse, when upward writing is done, air enters the refill through the clearance `h` between the ball `b` and the holder `d` and the ink flows toward the opposite direction to the ball `b`, causing a back leakage.
A main object of the present invention is to provide a ball-point pen capable of preventing the back leakage which is liable to occur when upward writing is done.
Other objects of the present invention will be apparent from a reading of the following detailed description with reference to the accompanying drawings.